For servers, e.g. connected to the Internet or other IP (Internet Protocol) networks, it is common that a particular server is only set up to serve requests where the requester meets some criteria e.g. of a user or of a geographic location or associated with a particular service provider.
In the prior art, such a server will still be called from invalid requesters who has no control of whether the request can be served or not. The server thus has to examine the request and determine whether to serve the request or not. In other words, even for requests that are not to be served, the server is required to perform a significant amount of processing, particularly if there are many such invalid requests.
It would of great benefit if there was a way to prevent such invalid requests from even reaching such servers.